It is desirable to have effective circuitry for controlling the starting and operation of 120 V or 240 V AC induction motors with a DC power input. An application of such a circuit is the use of a 12 volt DC power source, as may be available with a car or RV, to operate a compressor motor for a refrigerator available in or around the vehicle. Traditional systems include peak voltage varying circuitry or pulse width modulation.
However, adapting the use of such a DC power source to control such a motor encounters certain requirements, limitations and problems with traditional systems. The circuit would preferably be adaptable for use with either a DC input or an AC input, as may be available through an RV hookup connected to a typical 60 Hz AC source. The circuit should provide substantially greater peak current when the motor is started. Circuitry should be provided so that the large initial current load does not create problems such as excessive current drain from the DC source or inadequate power which stalls the motor. It is also desirable to develop a starting and control circuit for such a motor which addresses the above problems and limitations through the use of relatively fewer circuit elements to increase the reliability, decrease the cost, and increase the ease of repair of the circuit. Other desirable factors of such an apparatus include higher efficiency, lighter weight, and operability in a wide range of ambient temperatures.